Steering and roll-stabilizing device with retractable fins

ABSTRACT

The system includes at least two units each contained in a watertight housing to be installed on starboard and on port side, each containing inside a blade or a fin having a moving device that retracts or projects the fin outboard when necessary for steering or stabilizing. In both cases the blades or the fins are maintained normally inside their housing to reduce sailing resistance and are extended right or left only when activated for steering or for stabilizing. The motion device essentially consists of a plate joined to the blade or fin tilting on a shaft pivoting inside the housing but holding out at least one end passing through a hub provided with a seal providing water tightness and supporting actuators, and capable of supporting remote monitoring systems that record the exact position of the blade constantly and automatic controls of course or an automatic stabilization system.

On today's motorized craft, for steering, one or more traditionalrudders are used, generally consisting of a blade provided with atorsion shaft maneuvered from inside the hull. Similar system is usedfor stabilizing devices. Those kinds of appendages are normallymaintained immersed during navigation also when not utilized with thedrawback of a power consumption particularly on fast boats such as motoryachts, patrol vessels, catamarans etc, considering also that this powerconsumption increases not proportionally but with the square of speed.

Another drawback less evident but not less important that will be betterillustrated at the end of the present Description and in FIGS. 6, 7, 8,9 consists on the fact that, when sailing in rough sea, the action ofthe water on the rudder blade, usually oriented up to a maximum value of35°, creates, beside a drag, lifting forces perpendicular to thelongitudinal axis of the ship (FIG. 7) acting abaft alternatively on theport or starboard side, forcing the ship to follow a zigzagging course.This situation better named in the marine jargon “yawing” reduces speedand increases fuel consumptions a lot as any skipper well knows.

The system object of this invention will reduce such situation due tothe asymmetric drag force induced by the rudder operating only on theveering side. At the end of the '90s a steering system has been studiedand realized maintaining the rudders retracted on board during coursebut configured to be inserted into the water each time when necessaryfor steering. Naturally the immersed rudder was only that one inside theveering. The system was based on the fact that any watercraft having acompletely symmetrical keel and with balanced propulsive forces tends tokeep a constant direction of course if no extraneous forces such aswind, wave motion, current etc. intervene to change the direction ofnavigation.

Rudders based on these assumptions were activated only when required forlimited percentage times and also with limited incidences during thenormal steering on course, obtaining a considerable fuel saving.

On this basis a steering apparatus has been realized consisting of apair of retractable rudders installed abaft the boat outside the transomone on right side and one on left side immersed only when necessary toveering. (See p Application PCT E 518 229 A1 to Brighi/Harrauer)

This known kind steering device yielded favorable results in that awatercraft navigating in course with retractable rudders shows nogreater instability that conventional ones but with the considerableadvantage to save fuel especially at high speeds.

Nevertheless this kind of steering system was not generally appliedbecause of tradition in the marine field and because the installation ofthe equipment attached and projecting outside of the transom createdfear that some collision while backing to the quay might damage thesteering means.

On the basis of the obtained results a different version was found,essentially consisting of two units each contained this time in awatertight housing symmetrically installed inside the hull on port sideand on starboard side each provided with a retractable rudder bladeessentially connected to a prismatic guide element, vertically slidinginside a tubular housing movable by an actuator contained inside thecasing, so that it can be retracted or projected out to a variableextent in water as shown in FIG. 5. More details of this system arecontained in the doc. U.S. Pat. No. 7,434527 B2 October 2008 and EP1718522 both to Brighi.

This system also did not have diffusion on the market manly for tworeasons: the first one being that the considerable vertical dimensionsespecially for applications as anti rolling device requiring inside thehull, a certain space for the tubular shape of the housing containingthe blade, the prismatic guide and part of the actuator. The secondimportant reason consisted in the difficulty of bringing outside thehousing, in condition of absolute protection and safety, the monitoringsystems relative to the blade position necessary for the auto pilotsystem and automatic stabilization also. All these problems are resolvedby the system described herein.

This is in short the state of the prior art stage for steering systemsto our knowledge.

PRIOR ART CONCERNING STABILIZATION EQUIPMENT

The equipment object of the invention has the particularity to be usedalso as a stabilization device in conditions of rough sea but also incertain situations at high speed when the boat takes a swinging tendencycreating serious concerns on board.

The antirolling stabilization equipment of today consists generally in apair of fins similar to rudders outstanding on both sides of the boatunder water level, these fins rotating on their axis and automaticallymaneuvered from inside board being capable to create a torque opposed tothat torque created by rough sea.

This kind of fins in smaller craft is normally permanently maintainedoutside the board, being power consumption limited, while in faster andmore evolved craft a suitable chamber is provided where the entireapparatus can be totally retracted by mechanisms that are verycomplicated and expensive because the fin must receive in any case bothrotating and translating motions.

DESCRIPTION OF THE INVENTION

The system object of the invention is constructively the same whetherused for steering or for stabilization of the craft during navigation,and includes at least two units each contained in a watertight housingto be installed one on starboard side and the other on port side.Particularly in case of steering gear, the units will be placed withtheir vertical axis abaft the ship while, in case of stabilization gear,will be placed near the middle of the ship prevalently with a horizontalaxis. Each unit contains inside a blade (or a fin) provided with amoving device, capable to retract or to project the fin outboardpartially or totally when necessary for steering or for stabilizing,passing through the bottom of the housing where a suitable slot isprovided.

Such device consists essentially of a plate 2 joined together with thefin 1 and tilting on a shaft 4 pivoting inside the housing 3 but holdingout at least one end 5 passing through a hub 44 provided with a seal 49to maintain watertight the housing and at same time to receive a remotecontrol by any kind of electric or hydraulic actuator and at same timeto transmit remote information on fin position.

The system will better illustrated by the enclosed drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an exploded perspective representation of the unit to beinstalled on the portboard side (the starboard side unit issymmetrical).

FIG. 2 shows a vertical section in the middle plane of the same unit.

In these figures we can see that the blade 1 is characterized by havinga curvilinear profile, in order to permit an easy and complete outletfrom the watertight housing 3 obtaining a considerable volume reduction.The angle of incidence of the blade will be constant or variable alongthe axis of the blade according to boat features. The blade 1 joinedtogether to the plate 2 is tilting around the axis 4.

The housing 3/33, having prevalently a rectangular section, will bestructured in one, two or more parts to permit the assembly of theinternal components and to facilitate also the inspections whennecessary. The inferior section 3 could be less tall than the cover 33but sufficient to locate two side bearings 31/32 proportioned to supportall forces of lifting and drag generated from water action on the blade.

The same housing 3 will be provided on the base plate with a slot or anaperture 34 having appropriated dimensions to permit the passage of theblade.

The closure flanges 35 of the housing sections 3/33 will be connected bya series of bolts non shown in the figures after interposal of anadequate tested seal 49 capable of providing a perfect water tightness.

About the quality of the materials, a strong material such as stainlesssteel should be suggested for the inferior section 3 of the housingsupporting the forces transmitted from the plate appendages 21/22 on thebearing while for the section 33 having only cover function a fiberglass or aluminum material could be appropriate being light and notexpensive.

The inferior section of the housing 3 will be provided with appendageslike 36 to be coordinated with the shipyard in order to connect thehousings to the craft. In standard production the components 1-2-21-22-4can be realized in only one piece.

FIG. 3 shows in detail a section made in a horizontal planecorresponding to the control shaft axis 4 of the plate 2 where we cansee the following components: the shaft 4 joined to the plate appendages21/22 by spines 41/42 or similar connections while in case of standardproduction the components 1-2- 21 -22-4 can be realized in one piece.

The bearing 31/32 connected to the housing sides 3 will consistpreferably of two hubs 43/44 in order to facilitate assembling anddisassembling. Each is provided with long service bushing 46/47 capableof resisting sea water and supporting all forces of lifting and dragtransmitted by the blades. In case that the units will be used as astabilizing system and, with particularly heavy duty service, a pair ofrolling bearing could be used, properly protected.

The terminal hub 44 of the shaft 4 going outside of the housing 3 willbe provided with a seal 49 widely used and tested to maintain totalwatertight. On the same hub of the shaft 4 or eventually on the oppositeside a mechanical or electrical device transmitting a signal of theblade position may be installed, being this signal very important asfeedback for the electronic controls.

FIG. 4 shows an external view of one steering unit in a compact versionwhere the control shaft 4 sorting out of the housing is operated by thelever 5 from one hydraulic actuator 55 requiring a limited power becausethe forces to overcome are manly reduced to the friction forces actingon the bearing 46/47. On the cover 33 of the housing one hydraulic powerunit has to be installed that is completely connected to simplify theinstallation on board.

FIG. 5 shows in the same scale of the unit FIG. 4 an assembled view of aknown steering or stabilizing unit. It is characterized by a differentmovable system of the fin essentially requiring major encumbrance onboard specially in height and over all causing difficulties inobtaining, outside of the unit, the signal giving constantly the finposition. This is particularly important especially for automaticelectronic controls.

SYSTEM ADVANTAGES

The advantages consequential to the use of the described system are:

1—Lower fuel consumption or higher speed because the rudder blades orfins are retracted when they are not used.

2—Less fuel consumption sailing in rough sea due to the yawing reductionas represented in FIG. 7.

3—The asymmetric drag due to the single rudder exposed only inside theveering, see FIGS. 8 and 9.

4—The rudder exposed only inside the veering could be provided with ahydrodynamic profile having a better lifting feature than theconventional one requires a symmetric profile to work with both faces.

5—Reduced maneuvering forces on the actuators because the reactions ofthe water act all on a horizontal plane discharging the efforts manly onthe bushing of the plate supports.

6—Simplicity and low cost of the housing units particularly because itcould be easy standardized: 4 or 5 housing models could be cover a highrange of boats of different lengths and types considering that only therudder blades or the fins should be changed.

7—Easy and simple installation on board, also considering that thecouple of units are each independent without any mechanical connectionlike a rudder stock connecting rod etc., leaving free space for a cabin,tender lodgment etc.

1. An apparatus for steering or stabilization of a craft duringnavigation comprising: at least two units each contained in a watertighthousing configured to be installed one on a starboard side and the otherone on a port side, each unit containing therein a blade or fin providedwith a moving device configured to retract or to project the blade orfin outboard partially or totally when necessary for steering or forstabilizing, a slot being defined on the bottom of the housing, theblade or fin being maintained inside the housing to reduce sailingresistance, the blade or fin being protruded when actuated for steeringor for stabilizing, a gradual movement of the blade or fin beingobtained only by a degree of exposition or by an incidence angle and notby rotation on an axis of the blade or fin, a plate joined to the bladeor fin tilting on a shaft pivoting inside the housing but holding out atleast one end passing through a hub provided with a seal to maintain thehousing watertight and support an electric or hydraulic actuator workingin a water tight and protected place and to support a remote monitoringsystem recording an exact position of the blade of fin constantly andautomatic controls of course or an automatic stabilization system. 2.The apparatus as in claim 1, wherein the blade or fin has a hydrodynamicprofile constant or variable along the axis.
 3. The apparatus as inclaim 2, wherein the blade or fin has a top plate at its extremitycreating a limited asymmetric resistance on port or starboard side fornavigation at low speed.
 4. The apparatus as in claim 1 each unit,wherein the apparatus comprises more than one blade or fin connected tothe plate parallel and disposed as a biplane providing greaterefficiency with same dimensions.
 5. The apparatus as in claim 1, whereinthe units are placed with a vertical axis abaft the craft.
 6. Theapparatus as in claim 1, wherein the units are placed in a middleposition of the craft to provide greater stability.